The program is designed to continue a broad comparative approach to the study of a congenital abnormality of the visual pathways that characterizes albino mammals. The abnormal pathways will be defined by a variety of neuroanatomical tracing methods, which will reveal the abnormal pattern of the retinogeniculate projections and associated abnormalities o the geniculocortical, corticogeniculate and callosal cortico-cortical connections. This will reveal the extent to which it is possible to define a single characteristic albino abnormality for all mammals and the extent to which there may be interspecies differences. Using this background, the development of the retinogeniculate, geniculocortical and cortico-geniculate pathways will be studied in order to show how the appearance of the several abnormalities may be interrelated. The early development, intrauterine and postnatal, of the abnormality will be studied. The first appearance of the abnormal retinofugal pathways will be defined, the position and distribution of the abnormal fibers will be recorded as development proceeds, and the early appearance of the abnormalities of the suprageniculate pathways will be related to the development of the infrageniculate pathways. Finally, the degree to which the suprageniculate pathways, and the lateral geniculate nucleus itself, may be modified by an early monocular enucleation in an albino animal will be studied in order to define the extent to which the central pathways may be determined by the peripheral, retinal input. The study will initially use ferrets, rabbits, Siamese cats and guinea pigs.